A student once asked Ts' ui-wei “What is the real meaning of Buddhism?” Ts' ui-wei answered: "Wait until there is no one around and I will tell you." Later that evening the monk again approached him and said, "There is nobody here now. Please tell me, what is the real meaning of Buddhism?" Ts'ui-wei led him into the garden and went over to some bamboo and pointed. "Here is a tall bamboo; there is a short one!"
A fundamental tenet of Zen is that there are no hidden teachings. Everything is free and presented openly. Within these open teachings lie both the esoteric and exoteric teachings, only the student's understanding separates one from the other. Anyone who claims that there are hidden teachings beyond this, knows nothing of Zen.
Nothing is hidden!